1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a time sharing type autostereoscopic display apparatus and a method for driving the same, and more particularly, to a time sharing type autostereoscopic display apparatus using a hold type display such as a liquid crystal display (LCD) and a method for driving the same.
2. Description of the Related Art
Time sharing type autostereoscopic display apparatuses are autostereoscopic display apparatuses which display an image for a left eye and an image for a right eye alternately on the entire screen at a very fast time period and simultaneously provide separated images to the left eye and the right eye in synchronization with a display period of the image for the left eye and the image for the right eye. For example, in liquid crystal shutter glasses time sharing type autostereoscopic display apparatuses, a left-eye unit of liquid crystal shutter glasses transmits light and a right-eye unit of the liquid crystal shutter glasses intercepts light while a left-eye image is displayed. In addition, the right-eye unit of the liquid crystal shutter glasses transmits light and the left-eye unit thereof intercepts light while a right-eye image is displayed. However, the liquid crystal shutter glasses time sharing type autostereoscopic display apparatuses require a complicated device for synchronizing the liquid crystal shutter glasses and the display and a circuit for driving the same and have a disadvantage of very high costs.
U.S. Pat. No. 3,858,001 discloses a related art time sharing type stereoscopic display system having a mechanical structure in which a linear polarization plate 12 that reciprocally rotates on the entire surface of a cathode ray tube (CRT) display 11 at 90 degrees, as illustrated in FIG. 1. In the case of the stereoscopic display system illustrated in FIG. 1, the linear polarization plate 12 is reciprocally rotated so that the angle of the linear polarization plate 12 is changed while an image for a left eye (LE) is displayed and the angle of the linear polarization plate 12 is changed again while an image for a right eye (RE) is displayed. After that, two polarization plates 13a and 13b of polarization glasses separate the image for the left eye and the image for the right eye from each other, respectively.
In addition, U.S. Pat. No. 4,719,507 discloses another related art time sharing type stereoscopic image display system having an electro-optic structure in which a linear polarization plate 14 is fixed on the entire surface of a CRT display 11 and a polarization switch 15 is disposed on the entire surface of the linear polarization plate 14, as illustrated in FIG. 2. The polarization switch 15 is characterized in that the direction of polarization of an incident light is changed according to an applied voltage. Thus, in the case of the related art stereoscopic image display system of FIG. 2, a voltage applied to the polarization switch 15 is adjusted so that the polarization switch 15 changes the direction of polarization of the incident light to one direction while an image for a left eye is displayed. Then, the polarization switch 15 changes the direction of polarization of the incident light to another direction while an image for a right eye is displayed. After that, two polarization plates 13a and 13b of polarization glasses separate the image for the left eye (LE) and the image for the right eye (RE) from each other, respectively.
However, a problem exists in the related art in that cross-talk occurs in the above-described techniques. As illustrated in FIG. 3, a display system sequentially scans an image of one frame from upward to downward of a screen and allows an image of a next frame to be displayed on an upper portion of the screen while an image of a previous frame is displayed on a lower portion of the screen. For example, when a period in which one frame is completely scanned is T, the image for the right eye is displayed on the entire surface at time 0 and the image for the left eye is displayed on the entire screen at time T. However, since the image for the right eye is consecutively changed into the image for the left eye between time 0 and time T, the image for the left eye is displayed on the upper portion of the screen and the image for the right eye is displayed on the lower portion of the screen. As a result, a time when the image for the left eye and the image for the right eye share the screen exists. Thus, as illustrated in FIGS. 1 and 2, if the direction of polarization is changed with respect to an image on the entire display screen, cross-talk, in which the image for the right eye and the image for the left eye appear if they are not completely separated from each other but are mixed with each other, occurs.
To address the problem, International Publication No. WO 98/44746 suggests the use of a divided type polarization switch. The divided type polarization switch is a polarization switch having a plurality of segments divided in a longitudinal direction, and a voltage signal is applied to each of the segments in synchronization with an image scanning time of a CRT corresponding to each of the segments. Conventionally, a time when a voltage signal is applied to one segment is faster than the image scanning time of the CRT corresponding to the segment, because a slight transition period is needed until the polarization switch reaches a normal state.
FIG. 4 is a timing diagram illustrating a method for driving a 5-divided polarization switch of a related art time sharing type stereoscopic image display apparatus using a CRT. For example, it is assumed that each segment of the polarization switch changes the direction of polarization of an incident light so that the direction of polarization of an emitted light can be identical with a polarization plate for a left eye of polarization glasses when an applied voltage is high and so that the direction of polarization of the emitted light can be identical with a polarization plate for a right eye of the polarization glasses when an applied voltage is low. In addition, in FIG. 4, T denotes a period in which a screen is refreshed, B denotes a blank time required until the screen starts being scanned, and P denotes an instant when a phosphor of the CRT emits light. In a related art case in which the CRT is used as a display, polarization switching is set to start earlier by a time D than a time when an image starts being scanned. This is because it takes time for transition when the polarization switch is activated. In the case of the CRT in which the phosphor instantaneously emits light using an impulse manner, as illustrated in FIG. 4, a time for driving each segment of the polarization switch coincides with an image display time P for a left eye or right eye of the CRT corresponding to the segment. Thus, cross-talk does not occur.
The above-described related art techniques are concerned about the case where a CRT having a sufficiently high refresh rate as a display apparatus is used. However, since an LCD panel having a very high refresh rate has been recently developed, an LCD can be used as a display panel for a time sharing type stereoscopic image display apparatus, instead of a CRT. However, unlike the instantaneously light-emitting CRT, the LCD is driven as a hold type display panel in which a pixel is kept in a light-emitting state while the LCD is turned on. Moreover, the response speed of the LCD is slower than that of the CRT. Accordingly, when the LCD is used as a display apparatus with the above-described related art techniques, it is not possible to reduce the effect of cross-talk.